Vapor electric device



Aug. 19, 1947. ROSE 2,426,054

VAPOR ELECTRIC DEVICE Filed Feb. 27, 1945 wmussszs;

7 l NVENTOR I herberzfil Pose. LP W ATTORNEY Patented Aug. 19, 1947 VAPOR ELECTRIC DEVICE Herbert A. Rose, Pittsburgh 21, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 27, 1943, Serial No. 477,386 4 Claims. (01. 175-363) My invention relates to a vapor electric device and particularly to a control system for insuring initiation of a power are in the various valves of a make-alive type converter.

In the operation of vapor electric converters, particularly of the make-alive type, it has heretofore been customary to provide periodic control impulses for initiating the cathode spot in the individual valves at the beginning of each conducting portion of a cycle therein. With certain transformer connections and with certain operating conditions the main power are in a valve or group of valves may fail to pick up during the necessarily short interval in which the make-alive impulse is operative. In installations fed by transformers which operate in multiple groups such as double three phase, double bi-phase or other multiple grouping utilizing interphase windings the misfire in a single valve may nullify the excitation of the interphase windings and result in a lack of commutating potential at the normal commutating instant. One

or more of the valve groups may then back out and will only resume current conduction after the entire converter has been shut down and restarted. This results in some of the valves or valve groups becoming completely inoperative, with consequent loss in capacity and other ill effects.

According to my invention this difiiculty is avoided by providing an auxiliary source of excitation potential which will maintain the cathode spot for a predetermined interval after the control impulse has operated. I accomplish this by providing an auxiliary source of alternating current potential connected to the individual makealive electrodes of the separate valves. This alternating source of potential has a peak value which is insuflicient of itself to initiate a cathode spot but, which, after the cathode spot has been initiated, is sufficient to maintain the spot for the critical interval of time.

It is, accordingly, an object of my invention to provide a control system in which a cathode spot is maintained for a predetermined interval after it has been initiated.

It is a further object of my invention to provide a more reliable control system for a vapor electric valve.

It is a further object of my invention to provide a control system having a mainand auxiliary excitation source.

Other objects and advantages of my invention will be apparent from the following detailed description taken in conjunction with the accompanying drawing in which the figure is a schematic illustration of a vapor electric converter embodying my invention.

I In the illustrative embodiment of my invention an alternating current circuit I is connected to a direct current circuit I I by means of a rectifier transformer I2 which is connected to. the alternating current circuit by a suitable breaker 52 and to the direct current circuit by a circuit breaker 12. The rectifier transformer I2 has a plurality of phase terminals herein designated I to 6, these phase terminals being connected to the anodes I3 of vapor electric valves herein designated as Ia to 611.

Each of the vapor electric valves Ia to Sc comprises, in addition to the main anode I3, a cooperating vaporizablereconstructing cathode I4 of suitable material such as mercury and a makealive electrode I5 of high resistant material in contact withthe cathode I4. The make-alive electrode I5 is preferably provided either with a portion of substantially lower resistant material or with a metallic connection which may operate as an exciting electrode after the cathode spot has been initiated The cathode spots are initiated by supplying a control impulse of relatively steep wave front and of relatively short duration with respect to the Wave length of the alternating current supply from circuit I0.

While any suitable impulsing system may be utilized, I prefer to utilize an impulsing system of the so-Called wave distorter or reactor firing type in which any suitable source of alternating current, which may conveniently be a transformer I6 fed from the alternating current circuit III by an insulating transformer I! and controlled by circuit breaker 3|, supplies energy through a wave distortion system comprising a storage device preferably in the form of a capacitor 20 and having the current thereto controlled by means of an impedance such as a linear reactor 2|. The current flow'to the make-alive electrodes I5 is then determined by means of a non-linear impedance, preferably in the form of a saturable reactor 22.

The impulsing system of the wave distorter type produces a symmetrical Wave and the application to one or the other of a pair of electrodes I5 is determined by a polarity sensitive network including a unidirectional conductor 23 (usually of the so called dry type) in series with each makealive electrode and a further unidirectional conductor 24 in shunt around the make-alive electrode I5 and its series rectifier 23. The use of the.

polarity responsive network is desirable to prevent reverse current through the make-alive electrode I5 and also to reduce the energy losses in the excitation system, however the losses are of such small amount that the polarity responsive means would probably be'dispensed with when using make-alive electrodes I5 which were sub-- 'stantially undamaged by reverse current flow therein.

supplies make-alive impulses of sufiicient ampli- 3 tilde to create a cathode spot but of relatively short duration. The time at which the cathode spot is initiated may be determined by any suitable phase shifting device such as the induction phase shifter 25.

Under certain operating characteristics of the device the mere initiation of the cathode spot may not reliably initiate a discharge between the main anode l3 and cathode l4. For this reason I have provided an auxiliary source of excitation potential which is preferably in the form of a transformer 30 energized from any suitable source having a frequency similar to the frequency of the main alternating current circuit In and may very conveniently be the alternating current circuit 10.

The phase terminals of the auxiliary source 30 are connected to the make-alive electrodes l5 preferably between the series unidirectional con ductor 23 and the connection to' the make-alive electrode [5. In order to prevent reverse current flow through the make-alive electrode I5, I prefer to insert a unidirectional conductor 32 between the phase terminals of the auxiliary source and each of the make-alive electrodes 15.

After the impulsing system has operated to initiate the cathode spot, the auxiliary source 30 will maintain an excitation arc during the period through which the connected auxiliary terminal is positive. In order to prevent undesirable operation, I prefer to maintain the maximum potential of the auxiliary source 30 sufficiently low that it will not, of itself, initiate the cathode spot but of sufficient potential to maintain an are after the cathode spot has been initiated so that any delay in the establishment of the main arc will not cause a misfire in the valve undergoing excitation.

Where voltage control is desired it is preferable to utilize some form of phase shift in connection with the impulsing devices and I have herein shown the well known inductive type of phase shifter 25 but obviously any other type of phase shifting means may be utilized. Usually it is more desirable to have the auxiliary excitation substantially in phase with the main anode potential so that there is no danger of the excitation persisting into the normally nonconducting period. I have therefore shown the auxiliary source 30 connected to an excitation source such as an insulating transformer l1 ahead of the phase shifting means 25. The entire excitation system may be supported from any suitable source of alternating current of the desired frequency herein shown as an insulating transformer i1 energized from the line through a switching device 3|.

While for purposes of illustration I have shown and described specific embodiments of my invention, it will be apparent that changes and modifications may be made therein without departing from the true spirit of my invention or the scope of the appended claims.

I claim as my invention:

1. In an electric conversion system having a plurality of make-alive type valves an excitation system comprising a make-alive electrode for each of said valves, an impulsing system including a uniconductor device for applying periodic impulses of short duration to said make-alive electrodes, said impulses being of suflicient potential to reliably initiate a cathode spot in said valve, a source of auxiliary alternating exciting potential, the potential of said source being in- 4, sufficient to normally initiate a cathode spot in said valve and means including a unidirectional conductor for impressing half waves of the potential of said source on said make-alive electrodes.

2. An excitation system for a vapor electric device having alternate conducting and nonconducting intervals comprising an exciting electrode in contact with a main current carrying electrode of said device, a source of exciting current impulsing means energized from said source for producing impulses of steep wavefront and short duration with respect to the conducting interval of said device, circuit means including a unidirectional conductor for impressing said impulses on said exciting electrode, an auxiliary source of alternating exciting potential, a second circuit means independent of said first mentioned circuit means for periodically impressing the potential of said auxiliary source on said exciting electrode, said second circuit means including a unidirectional conductor.

3; An electric current conversion system for transferring electric energy between dissimilar electric circuits at least one of which is an alternating current circuit there being at least a pair of alternating conducting vapor electric valves connected to control current flow between said circuits, each of said valves including a main anode and cathode and an exciting electrode in contact with the cathode, an exciting system for said valves comprising a source of alternating control potential, circuit means connected between said source and said exciting electrodes for periodically applying current impulses from said source to said exciting electrode, an auxiliary source of exciting current, and circuit means independent of said first mentioned circuit means for periodically applying the potential of said auxiliary source to said exciting electrodes, and circuit means in shunt with said exciting electrode for relieving the flow of reverse current therein.

4. An excitation system for a converter having at least a pair of alternating conducting vapor electric valves of the make-alive type comprising a make-alive electrode for each of said valves. 9. source of exciting potential, a wave distorting network connected between said source and said make-alive electrodes for applying to said make-alive electrodes impulses of steep wave front and short duration, polarity selective means including a unidirectional conductor in series with each of said make-alive electrodes for alternately applying said impulses to the respective make-alive electrodes, an auxiliary source of periodic exciting potential and connecting means including a unidirectional conductor for simultaneously impressing the potentials of said auxiliary source and said wave distorting network on one of said make-alive electrodes.

HERBERT A. ROSE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,221,615 Slepian Nov. 12, 1940 2,222,620 Klemperer Nov. 26, 1940 2,291,092 Cox et a1 July 28, 1942 2,310,101 Lord Feb. 2, 1943 

